Voice-over Internet Protocol (VoIP) has become popular and prevalent for communications. When a communication between two peers occurs, a session is created for the communication. As VoIP networks evolve into large end-to-end networks, messages, such as session initiation protocol (SIP) messages, increasingly have to traverse a larger number of intermediate hops before reaching a final end point. With unpredictable IP network delays and packet loss, the chances of losing a SIP message are high. This occurs especially if user datagram protocol (UDP) or any other unreliable protocol is used to send messages. When a SIP message is lost, this may lead to a hanging SIP session. A hanging SIP session is a session on one side of the communication that a peer thinks is active but is not active on the other side.
To address the issue of hanging SIP sessions, session refresh mechanisms are used. A SIP session is refreshed by sending SIP messages periodically. Refreshes in SIP can be expensive particularly if there is no change to a session. SIP sessions may be refreshed by sending messages typically used in a dialog, such as UPDATE, reINVITE, OPTIONS/200 OK, etc. These in-dialog messages are sent as a ping to see if the session is still active. If a response is received, then it is assumed the session is active. These messages are typically bulky in that they include a full header and body (e.g. session description protocol (SDP) or extensible markup language (XML) information). This is because they were not designed for a refresh. Rather, they were originally designed to perform other functions and thus, the format and requirements for content to be included in the messages do not take into account a mechanism for a pure refresh. For example, an INVITE message is typically used to request a connection to a device. However, the reINVITE message may be used to refresh a session in that the reINVITE message is sent for a session and if a response is received for the reINVITE message, such as a 200 OK message, it is assumed the session is active. SIP requires that the reINVITE message include certain fields in the header and also an SDP.